Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < - Mailing list pgsql-committers

From Kevin Grittner
Subject Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <
Date
Msg-id CACjxUsM0csE2vUw6p2fsVVv9W+WN3z+RhGXcw+BG0_FfVo_cvA@mail.gmail.com
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In response to Re: [HACKERS] Re: pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <  (Alvaro Herrera <alvherre@2ndquadrant.com>)
List pgsql-committers
On Wed, Jun 15, 2016 at 1:54 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Robert Haas wrote:

>> The expression index case is the one to worry about; if there is a
>> problem, that's where it is.  What bothers me is that a function used
>> in an expression index could do anything at all - it can read any
>> table in the database.
>
> Hmm, but if it does that, then the code that actually implements that
> query would run the STO checks, right?  The analyze code doesn't need
> to.

Right.  In the described case, you would get a "snapshot too old"
error inside the expression which is trying to generate the index
value.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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